耦合工况下的空气悬架车高观测和控制算法研究

Electronic controlled air suspension systems are able to actively adjust the vehicle height to improve the cross country performance and high-speed stability. But most of the adjustment has to be operated on the flat road or in the stationary conditions. It's hard to guarantee the control accuracy while running on the bad road. This has become the key obstacle for improving the air suspension performance and popularity. Aiming at the vehicle height observing and accurate control theory for air suspension system running on the bad road, this project will mainly focus on the research of the vehicle height observing and control algorithm for those working in the coupling conditions of road input and air charge/discharge progress. Firstly, through the experiment and theoretic analysis of the nonlinearity of various parts in air suspension system, the coupling mechanism between road input and air charge/discharge condition on the air suspension system will be deeply studied. Then, based on the nonlinear states observing theory, a sliding mode observing algorithm will be designed to observe the real vehicle height in the coupling condition of road input and air charge/discharge process. Then the feedback linearization output function and coordinate transfer frame will be designed, based on the differential geometry theory, to accurately linearize the coupling nonlinear system. The linear optimal control algorithm will be designed in the linear domain and then transferred back to the nonlinear domain. Finally, based on the hardware-in-loop simulation platform, the vehicle height observing and control algorithm for air suspension in coupling conditions will be tested and certified. This research work will provide the theoretic and technical foundation for the domestic development of the high performance electronic controlled air suspension system.

电控空气悬架能够主动调整车辆高度，提高恶劣路面通过性和高速行驶稳定性，但大多只能在良好路面行驶或静止时进行调整，在恶劣路面行驶时进行调整难以保证控制精度，成为制约电控空气悬架性能提升与推广应用的关键问题。 针对空气悬架在恶劣路况的车高观测和精确控制等核心问题，项目将着重开展路面激励与充放气耦合工况的空气悬架车高观测和控制算法研究。 首先，通过空气悬架各部件特性试验与分析，建立路面激励与充放气耦合工况下的空气悬架非线性数学模型；进而，基于非线性状态观测理论，设计滑模观测算法，实现耦合工况下的车高观测；然后，基于微分几何理论，设计反馈线性化坐标变换系，实现非线性系统的精确线性化，在线性空间中设计最优控制算法，并将最优控制函数逆变换至非线性空间中；最后，基于半实物仿真平台，对耦合工况下的空气悬架车高观测和控制算法进行验证。研究将为自主研发高性能电控空气悬架系统提供理论与技术基础。

项目针对空气悬架系统在路面激励和充放气过程耦合作用下的车高控制问题，开展了耦合工况下的车高观测和控制算法研究。.首先，分别建立了路面激励和充放气过程单一工况下的空气悬架非线性模型，以空气弹簧压力梯度方程为契合点，将空气悬架系统的非线性振动模型和充放气非线性模型进行联立，得到了空气弹簧内部压力梯度统一方程，通过统一方程可以同时体现出路面激励和充放气过程耦合作用对空气弹簧内部压力影响；.进而，基于得到的统一方程，将表征车身高度的悬架静平衡位置推导为状态变量之一，并整理得到空气悬架整车的非线性状态方程，根据非线性状态观测理论，设计了无迹卡尔曼状态观测器，以实时测得的悬架动挠度以及空气弹簧瞬态压力作为状态观测算法输入量，实现了耦合工况下车高观测算法对悬架静平衡位置的精确估计；.然后，针对非线性系统方程，构造反馈线性化输出函数，依据输出函数建立坐标变换系，在坐标变换后的线性域内，将车高观测值与目标车高值的误差为零作为控制目标，以电磁阀开启比例作为控制输出量，设计线性域内的车高控制算法，并反馈至非线性域中，通过联合仿真验证了基于车高观测的耦合工况下车高控制算法的可行性和鲁棒性，该算法能够在路面扰动存在时，精确控制车身高度；.最终，基于装备了空气悬架的乘用车进行了静止工况和随机路面行驶工况下的车高观测与控制算法的实车道路试验，并采用了车辆姿态测量单元辅助采集车高控制过程中的车身姿态。实车试验表明，所提出的耦合工况下车高观测和控制算法能够有效提高车辆静止工况和随机路面行驶耦合工况下的车高控制精度，减少路面扰动对车高控制过程的影响，减少车高控制过程中由空气弹簧非线性及迟滞性导致的超调现象。